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  1. #1
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    Default Visqueen attached to floor joists

    This is under a refrigerated wine storage room, as viewed from the foundation crawlspace area. The floor framing consists of I-joists and OSB sheathing. The bays between the joists have a standard R-19 fiberglass batt insulation. However, stapled to the underside of the joists is a 4 or 6 mil barrier. Now, I understand the builder's thought behind this. Since the room will be chilled to a temperature that is lower than you would normally cool a room, the framing would be more likely to be below the dew point and allow moisture to condense on the framing, which would set-up conditions conducive to fungus and rot. My concern is that this plastic sheeting would trap any moisture in the joist bays, creating the same condition. Summertime humidity in my area is relatively low, but winters are fairly humid and condensation problems typically occur during the winter.

    So... to whom would I defer? An insulation contractor? A refrigeraton contractor?

    Sorry about the quality of the pics. It is difficult to mimic Ansel Adams when I am lying on my side in an 18" space.

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  2. #2
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    Default Re: Visqueen attached to floor joists

    .
    Gunman,

    What's the ( fan? ) connected to or it's function?
    .

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  3. #3
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    Default Re: Visqueen attached to floor joists

    Billy,

    No fan in that pic. Not sure what you see. There is a ducted fan in the crawlspace area, but not in either of the pics that I originally posted.

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  4. #4
    Ted Menelly's Avatar
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    Default Re: Visqueen attached to floor joists

    Quote Originally Posted by Gunnar Alquist View Post
    This is under a refrigerated wine storage room, as viewed from the foundation crawlspace area. The floor framing consists of I-joists and OSB sheathing. The bays between the joists have a standard R-19 fiberglass batt insulation. However, stapled to the underside of the joists is a 4 or 6 mil barrier. Now, I understand the builder's thought behind this. Since the room will be chilled to a temperature that is lower than you would normally cool a room, the framing would be more likely to be below the dew point and allow moisture to condense on the framing, which would set-up conditions conducive to fungus and rot. My concern is that this plastic sheeting would trap any moisture in the joist bays, creating the same condition. Summertime humidity in my area is relatively low, but winters are fairly humid and condensation problems typically occur during the winter.

    So... to whom would I defer? An insulation contractor? A refrigeraton contractor?

    Sorry about the quality of the pics. It is difficult to mimic Ansel Adams when I am lying on my side in an 18" space.
    Whine storage room at what, 55 degrees or so. I don't know if that would be a big concerns. Humidity in the crawl with a fan to the exterior set up on a humidistate I would say no, it would not be a problem. I think the plastic may cause more of a concern holding moisture inbetween the plastic and OSB. Could be wrong. Depending on the temp outside and the humidity level with the floor being cool also from the wine storage room as well should not make a concern. Temp in the crawl in the summer will still be cooler than the exterior temp. I just don't see where the sheeting is doing anything but harm.

    Please let me know what the pros say. I am truly interested.

    Ted Menelly, Castle Home Inspection Services
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  5. #5
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    Default Re: Visqueen attached to floor joists

    Quote Originally Posted by Gunnar Alquist View Post

    Billy,. Not sure what you see..
    .
    That thingy ( technical term ) with those Yellow thingies running to it in the corner.
    .
    .

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  6. #6
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    Default Re: Visqueen attached to floor joists

    Gunnar,

    Tried to post link but

    Check this Section Your Post is in ( Sub Structure,)

    scroll down to Vapor barrier by Mathew Stouffer,

    last post Jerry Peck 8-19-2008.

    *I'm thinking the vapor barrier would collect moisture.

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  7. #7
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    Default Re: Visqueen attached to floor joists

    Gunnar, I don't know what your temps. and humidity are but think back to your average dew point summer and winter. If the wine cooler is colder than the dew point more than half the year, then vapor barrier there may be a good thing BUT you don't want vapor barriers on both the inside and the outside. The wall (or floor in this case) needs to be able to dry to one side or the other.
    I think Dr. Joe has some info about this on the Building Science web site.
    The old adage of putting the vapor barrier on the "warm in winter" side does not work in special circumstances like this, you need to look at the physics of what is driving the water vapor through the wall assembly and which direction it is being driven.
    What type of floor covering did they have?

    Jim Luttrall
    www.MrInspector.net
    Dallas, Texas

  8. #8
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    Default Re: Visqueen attached to floor joists

    Quote Originally Posted by Billy Stephens View Post
    .
    That thingy ( technical term ) with those Yellow thingies running to it in the corner.
    .
    Billy,

    The yellow thingies are NM cable (you probably knew that) and the silver is flex heater duct. The plastic is hanging down at the far end of the pic.

    Thanks for the clue to the previous post. I had thought I remembered something like that, but I guess I did not do a good enough search.

    Last edited by Gunnar Alquist; 06-25-2009 at 11:44 PM.
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  9. #9
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    Default Re: Visqueen attached to floor joists

    Quote Originally Posted by Jim Luttrall View Post
    What type of floor covering did they have?
    Jim,

    The floor is ceramic tile. Not very permeable, but my concern is that I feel that moisture is still likely to get in and not be able to get out.

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  10. #10
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    Default Re: Visqueen attached to floor joists

    Gunnar, I am thinking that about 9 months out of the year 55 degrees would be cooler than the outdoor temp in my area. I don't know what relative humidity they maintain in the cooler, but at 50%, I am thinking that the moisture movement is moving from outdoors to indoors at least 9 maybe 10 months out of the year with little movement at all the rest of the year.
    So for my area, vapor barrier on the outside with a permeable inner surface would be the design to shoot for.
    To Quote Dr. Joe Lstiburek from his book Builder' Guide for Hot-Dry and Mixed dry climates, "Vapor barriers on the interior of wall assemblies and roof assemblies are not recommended in hot-dry climates."
    I realize that you are likely not in a hot-dry climate, but the point is that interior vapor barriers are not called for in all situations and you have to look at the both the climate and the design conditions.
    Have not answered your question, but maybe this is food for thought.

    Jim Luttrall
    www.MrInspector.net
    Dallas, Texas

  11. #11
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    Default Re: Visqueen attached to floor joists

    So... to whom would I defer? An insulation contractor? A refrigeration contractor?
    I would go with a refrigeration contractor. They are more likely to understand the complex relationship than most anyone.

    Jim Luttrall
    www.MrInspector.net
    Dallas, Texas

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